The Role of Weak Links and Zn-Doping on Magnetic Parameters of High-T_c Superconductors

摘要

The second harmonic signal, which is generated by co-application of AC and DC fields to polycrystalline type-II superconductors, were analyzed in terms of the weak links and the critical current density. With this aim the YBa_2Cu_(3-x)Zn_xO_(7-y) (x = 0, 0.01, 0.02, 0.03, 0.05, and 0.1) samples were synthesized in order to adjust intergranular couplings and thus the strength of weak links. The mechanical and magnetic measurements are in good agreement on that Zn doping reduces strength of the links between grains; however, contrary to the common expectations, it has no direct contribution to the 2nd harmonic signal strength.